Difference between revisions of "cpp/algorithm/move backward"
From cppreference.com
(Add header above declaration) |
m (Uses {{dcla}} with the “constexpr” parameter.) |
||
| Line 3: | Line 3: | ||
{{dcl begin}} | {{dcl begin}} | ||
{{dcl header|algorithm}} | {{dcl header|algorithm}} | ||
| − | {{ | + | {{dcla|anchor=no|since=c++11|constexpr=c++20| |
template< class BidirIt1, class BidirIt2 > | template< class BidirIt1, class BidirIt2 > | ||
BidirIt2 move_backward( BidirIt1 first, BidirIt1 last, BidirIt2 d_last ); | BidirIt2 move_backward( BidirIt1 first, BidirIt1 last, BidirIt2 d_last ); | ||
Latest revision as of 01:34, 15 August 2024
| Defined in header <algorithm>
|
||
template< class BidirIt1, class BidirIt2 > BidirIt2 move_backward( BidirIt1 first, BidirIt1 last, BidirIt2 d_last ); |
(since C++11) (constexpr since C++20) |
|
Moves the elements from the range [first, last), to another range ending at d_last. The elements are moved in reverse order (the last element is moved first), but their relative order is preserved.
If d_last is within (first, last], the behavior is undefined. In this case, std::move may be used instead.
Contents |
[edit] Parameters
| first, last | - | the range of the elements to move |
| d_last | - | end of the destination range |
| Type requirements | ||
-BidirIt1, BidirIt2 must meet the requirements of LegacyBidirectionalIterator.
| ||
[edit] Return value
Iterator in the destination range, pointing at the last element moved.
[edit] Complexity
Exactly std::distance(first, last) move assignments.
[edit] Possible implementation
template<class BidirIt1, class BidirIt2> BidirIt2 move_backward(BidirIt1 first, BidirIt1 last, BidirIt2 d_last) { while (first != last) *(--d_last) = std::move(*(--last)); return d_last; } |
[edit] Notes
When moving overlapping ranges, std::move is appropriate when moving to the left (beginning of the destination range is outside the source range) while std::move_backward is appropriate when moving to the right (end of the destination range is outside the source range).
[edit] Example
Run this code
#include <algorithm> #include <iostream> #include <iterator> #include <string> #include <string_view> #include <vector> using container = std::vector<std::string>; void print(std::string_view comment, const container& src, const container& dst = {}) { auto prn = [](std::string_view name, const container& cont) { std::cout << name; for (const auto &s : cont) std::cout << (s.empty() ? "∙" : s.data()) << ' '; std::cout << '\n'; }; std::cout << comment << '\n'; prn("src: ", src); if (dst.empty()) return; prn("dst: ", dst); } int main() { container src{"foo", "bar", "baz"}; container dst{"qux", "quux", "quuz", "corge"}; print("Non-overlapping case; before move_backward:", src, dst); std::move_backward(src.begin(), src.end(), dst.end()); print("After:", src, dst); src = {"snap", "crackle", "pop", "lock", "drop"}; print("Overlapping case; before move_backward:", src); std::move_backward(src.begin(), std::next(src.begin(), 3), src.end()); print("After:", src); }
Output:
Non-overlapping case; before move_backward: src: foo bar baz dst: qux quux quuz corge After: src: ∙ ∙ ∙ dst: qux foo bar baz Overlapping case; before move_backward: src: snap crackle pop lock drop After: src: ∙ ∙ snap crackle pop
[edit] See also
| (C++11) |
moves a range of elements to a new location (function template) |
| (C++20) |
moves a range of elements to a new location in backwards order (niebloid) |
